COMPACTING MUNICIPAL SOLID WASTE INTO "LOGS" FOR COMBUSTION AT COAL-FIRED POWER PLANTS

This paper is based on the findings of a research project entitled "Compacting Biomass and Municipal Solid Wastes to Form an Upgraded Fuel," sponsored by the Federal Energy Technology Center (FETC), U.S. Department of Energy. High-pressure compaction of various types of waste paper and plastics found in municipal solid waste were studied. A piston-and-mold (punch-and-die) process was used and compaction was performed without binder under room temperature and at pressures ranging from 69 to 138 MPa. The waste materials were compacted into 49-mm-diameter logs both separately and in mixtures. The effects of compaction pressure, moisture content and composition of the feedstock on the product - logs were studied. The density, abrasion resistance, impact resistance, and combustion characteristics of the logs made were tested. It was found that all the papers can be compacted into good logs under pressure of 100 MPa. Paper mixture with moisture content ranging from 5% to 20% can be easily compacted into logs of good quality under pressures above 70 MPa. When the pressure is above 100 MPa and the moisture content of the waste paper is lower than 10%, logs with dry densities greater than 1 g/cm³ can be produced. The optimum moisture content for making abrasion-resistant and impact-resistant logs is in the neighborhood of 15%. Although plastics are difficult to compact into good logs, by mixing plastics with waste paper, good logs can be made. It was found that a mixture of paper and plastic film containing up to 15% LDPE or HDPE film can be compacted into good logs with dry densities above 0.8g/cm³ and high abrasion and impact resistance.